TeamViewer Corporate - How to assign all available channels to channel groups?

Hey guys,

we have 4 channel in our corporate TeamViewer account. I created a channel group and tried to assign those 4 channel to that group - but that wasn't possible. The following error message appeared:

I only was able to assign 3 of 4 channel:

But why? Is there no way to assign all channel to one or more channel groups?

We plan to buy more channel and add more user and different groups - but of course, we don't want to waste channel!